A heavy-duty Rotork EH electro-hydraulic linear actuator has solved an expensive and repetitive valve operating problem at the Entergy Willowglen power station in Mississippi, USA. The valve – an Edward Class 2500 14″ x 12″ x 14″ high-pressure non-return globe control valve on boiler feed water pump discharge service – was motorised with an obsolete electric actuator that was no longer supported by its manufacturer. The actuator was regularly causing self-inflicted damage to its drive bush and gearbox when the valve was operated, forcing the station to repair it on an annual basis. Because all the required replacement parts were not available from the manufacturer, they had to be specially made, dramatically increasing the repair cost. Seeking a solution to the problem, Entergy contacted Rotork. Rotork’s suggestion was to replace the electric actuator with an EH range electro-hydraulic linear unit – customised for the plant’s requirements – which would utilise the same electrical power supply but operate the valve hydraulically, providing the swift and responsive actuation required without the risk of damage to either valve or actuator. Modifications were also made to increase the actuator’s manual override operating speed before the unit was fitted in the middle of 2001, since when it has been providing reliable and problem-free service.
